The invention relates to a pyrodetector for the detection of a body entering into its detection area and wherein the body has a temperature deviating from its environment. A concave mirror or concentrating reflector for focussing the heat radiation emanating from the body is provided along with a first sensor element at the focus of the concave mirror. At least one further sensor element is provided for the compensation of environmental influences. A film of uniform electrically nonconductive material, particularly polyvinylidene di-fluoride, and having an isodirectional permanent orientation polarization with electrodes situated thereon is provided for the first and further sensor elements. This arrangement is secured in a mounting also containing a cover of the mirror cavity transmissive for the incident radiation and an electronic evaluation means. The film with the sensor elements is arranged in the concave mirror such that a radiation incidence of the radiation reflected in the concave mirror is present on both surface sides of the film. The concave mirror is a parabolic mirror dimensioned such that its focus lies in the inner half of the concave mirror. Thus, the film with the sensor elements is at the optical axis of the concave mirror so that the first sensor element is essentially impinged only by a radiation of the detectable body situated at a greater distance which has been reflected in the concave mirror. A thin film of polyethylene is employed as a covering, this film being stretched over a honeycomb lattice acting as a support which is arranged preceding the mirror cavity.
A pyrodetector comprising these features has been set forth in detail with respect to its structural design and, in particular, with respect to its functioning in EP-E1 U.S. Pat. No. 0,023,354. This European patent corresponds to German Pat. No. 29 30 632 together with German OS Pat. No. 30 28 252, as well as to U.S. Pat. No. 4,404,468, incorporated herein by reference.
A preferred embodiment of the thin film of polyethylene serving as a covering is set forth in the German patent application P 35 32 475.9.
A particularly preferred structural design for the arrangement of the sensor elements in a retaining frame and a method for the manufacture thereof are set forth in the German patent application P 35 32 454.6.